The present invention relates to an overflow protection device. Specifically relates to an overflow protection device for a pressurized gas tank.
Pressurized gas tanks are often used for containing liquid propane, but the present invention relates to tanks which may contain other gases that are under pressure to the point where they are in a liquid form.
Many of these gases expand substantially by volume for every 10xc2x0 F. to which the tank is exposed. For example, liquid propane expands at approximately 1.5% by volume per 10xc2x0 F. Propane tanks are designed so that when they contain the specified weight of propane at 60xc2x0 F., approximately 20% by tank volume remains available for expansion of the liquid. The present invention is intended to ensure the tanks are not filled beyond this expansion space.
Overflow protection valves currently available and in widespread use do not necessarily ensure this protection. They often contain excessive numbers of operating and sealing components. Also they are often gas pressure operated and therefore performance depends upon pressures created by the fill equipment. Performance is also subject to false triggers where with rapid and fast start up of incoming gas the overflow protection valves accidentally shut down. Many overflow protection valves are of large diameters that interfere with the outage tube extending from the bottom of the main supply valve.
Therefore, a primary object of the present invention is the provision of an improved overflow protection valve and method for operating same.
A further object of the present invention is the provision of an overflow protection device that utilizes a simple ball/seat design, thereby eliminating gas driven pistons.
A further object of the present invention is the provision of a valve that eliminates the use of elastomeric components which often become damaged or corroded as a result of exposure to certain gases.
A further object of the present invention is the elimination of springs used in prior overflow protection devices.
A further object of the present invention is the provision of an improved overflow protection device which eliminates the elastomeric seals that often can be contaminated with oils, rust and water found within the propane that quickly degrade the seal integrity and thereby cause a loss of pressure or high co-efficient of friction between the seal and the cylinder.
A further object of the present invention is the provision of an improved overflow protection device that eliminates gas driven pistons that impede the flow of incoming liquid, but to do so require a central gas port to direct energy under the piston for its moving power.
A further object of the present invention is the elimination of gas pressure ports used to port vacuum or pressure to the usable side of a piston. Usually these ports are in the 0.050 to the 0.060 diameter range and are subject to plugging by rust and other particulate matter naturally present in propane.
A further object of the present invention is the provision of a reduction in the diameter of the valve, thereby eliminating interference normally encountered with the main supply valves outage tube.
A further object of the present invention is the provision of a ball retainer that serves three distinct functions: 1) It prevents the ball from elevating during gas discharge and blocking or impeding the flow of gas through the inlet and vapor port. 2) The legs of the ball retainer provide a cage to control the ball axially above the seat and in approximate vertical alignment with the ball lift pin thereby reducing side loading on the lift pin. 3) A convex top directs incoming liquid around the ball reducing the frictional loading on the ball and subsequently on the operating mechanism. There are four ribs that provide space for incoming liquid to pass around the retainer and which prevent the expansion of the incoming liquid to vapor until after the liquid is below the center line of the ball. This results in lowered pressure below the ball, and when the ball is free to move downwardly it will do so in response to this pressure differential.
A further object of the present invention is the positioning of the exhaust ports as high as possible in the tank so as to prevent liquid propane from entering the ports during appliance use of the propane within the tank, particularly when the tank is exposed to high temperature.
A further object of the present invention is the provision of a lower body design that incorporates exhaust ports that are oriented at 90xc2x0 to the float arm""s operating plane, thereby directing the incoming propane away from the float.
A further object of the present invention is the provision of a ball/seat arrangement that in concert provide a valve that operates at all pressures, especially those in very low pressure ranges.
A further object of the present invention is the provision of a valve that upon failure permits the valve ball to naturally fall into the seat, thereby preventing fill and requiring service.
A further object of the present invention is the provision of a valve that provides extremely high flow rates of both vapor and gas in both directions.
A further object of the present invention is the provision of an improved valve that is economical to manufacture, durable in use, and efficient in operation.
The foregoing objects may be achieved with an overflow protection device that includes a valve body having a gas conduit extending through the valve body. The gas conduit comprises a conduit inlet opening for introducing pressurized gas, a conduit outlet opening for permitting the pressurized gas to exit, and a valve chamber between the conduit inlet opening and the conduit outlet opening. A valve is within the valve opening and is mounted for movement from a closed position preventing pressurized gas from passing from the conduit inlet opening to the conduit outlet opening to an open position permitting pressurized gas to pass from conduit inlet opening to the conduit outlet opening. The valve is biased to the closed position by the pressure of the pressurized gas from the conduit inlet opening. A float is movably mounted to the valve body. A cam is associated with the float and is movable in response to the movement of the float between a full position and a less than full position. An actuator is mounted for movement within the valve body and is in engagement with the cam. The actuator is movable in response to the movement of the float to the less than full position to engage the valve and hold the valve in the open position. The actuator is movable in response to movement of the float to the full position to withdrawn from the valve and permit the valve to move to the closed position.
According to another feature of the present invention, a valve retainer is positioned between the valve and the conduit inlet opening of the valve body.
According to a further feature of the present invention, the valve retainer includes a valve cavity partially surrounding the valve.
According to another feature of the present invention, the valve includes four sides surround the valve cavity. A first two of the four sides are adjacent one another and have a first length. A second two of the four sides are adjacent one another and have a second length less than the first length, so as to imbalance the pressure on the ball and bias it to its closed position when the actuator is withdrawn.
According to another feature of the present invention, at least one of the first two of the four sides includes a lower edge having a notch formed therein.
According to another feature of the present invention, the valve cavity is partially spherical in shape and the valve is a ball.
According to another feature of the present invention, the actuator comprises a pin and the valve body includes a pin bore loosely housing the pin. A pin includes an upper end within at least a portion of the conduit between the valve and the conduit outlet opening.
According to another feature of the present invention, the float and the cam are rigid with respect to one another so that the cam moves in unison with the float.
According to another feature of the present invention, the cam includes a first cam surface engaging the actuator during the time that the actuator holds the valve in an open position and includes a second cam surface engaging the actuator during the time that the actuator permits the valve to move to its closed position.
While the above invention may be utilized in combination with a pressurized gas tank for any of a plurality of gases, the preferred form of the invention is for use with a propane gas tank.
The foregoing objects may be achieved by the method of the present invention by connecting a valve body within the gas chamber to the gas inlet opening. The valve body includes a conduit comprising a conduit inlet end in communication with the gas inlet opening, a conduit outlet opening for introducing pressurized gas into the gas chamber, and a valve chamber between the inlet opening and the outlet opening.
The method further comprises positioning a valve in the valve chamber, the valve being movable from an open position permitting the pressurized gas to flow from the conduit inlet opening through the conduit outlet opening to a closed position preventing the pressurized gas from flowing from the conduit inlet opening to the conduit outlet opening. A float is mounted to the valve body for movement from a less than full position to a full position, the float having a cam surface thereon. An actuator is engaged with the cam surface. The actuator has a first end engaging the cam surface and a second end positioned adjacent the valve. The method includes moving the actuator to engage the valve and hold the valve in the open position in response to movement of the float and the cam to the less than full position.
The method further comprises moving the actuator to withdraw from engagement with the valve so as to permit the valve to move to the closed position in response to movement of the float and cam to the full position. The valve is biased to its closed position. However, the valve is always free to move to its open position by being pushed upwardly out of the way of discharging gas.